This invention relates to panel assemblies, and more particularly, to window panel assemblies having a gasket mounted on one or more sides of a sheet of glass or plastic and used as a panel or window in a vehicle, building or other structure, as well as a method for making such window assemblies. Such window assemblies are commonly known in the vehicle industry as "modular windows."
Modern modular vehicle windows include a gasket attached by molding or extrusion directly onto the glass panel. In manufacturing molded, modular window panels, a sheet of glass is closed within a molding tool, and a polymeric material is injected around the peripheral edge on opposing surfaces or on a single surface of the sheet edge, thereby attaching the polymeric material to the peripheral edge of the glass panel. After the material is cured, the mold is opened and the panel assembly is removed. To retain the modular window assembly within the vehicle, studs or clips may be molded within or attached to the gasket and panel and used to engage the pinch weld flange forming the vehicle opening. Alternately, or in addition thereto, a bead of adhesive can be applied to bond the panel assembly directly to the pinch weld flange.
One category of modular windows includes assemblies having an exposed peripheral edge on the glass panel known as "flush-mounted" window assemblies. One such flush-mounted vehicle includes an extruded gasket of thermosetting material deposited directly on the surface of a glass sheet. In other assemblies, the extrusion includes two adhesive beads of polyurethane compounds, one deposited by the panel assembly manufacturer and the other applied by the vehicle assembler. Such assemblies require a long cure time for the first bead, adding cycle time to manufacturing. In addition, the gasket material used in the forming the extruded gasket is typically not ultraviolet radiation stabilized by itself and can degrade over time upon exposure to the elements. Moreover, the extrusion process does not easily adapt itself to receiving mounting studs or clips, or to forming in variable cross sections. Extrusion is also expensive, and requires special storage and handling after manufacture.
Other window assemblies intended for use in flush-mounted applications include a gasket of thermosetting material molded directly to a single surface of panel in a molding machine using reaction injection molded (RIM) urethane. Although variable cross sections can be formed using this method, RIM urethane gaskets still degrade when subjected to prolonged exposure to UV light, require a long cycle time during manufacture, and have increased material costs compared with other materials. In addition, it is often found that the tension or shear force applied to the glass and RIM molded gasket results in failure of the adhesive seal between the gasket and the glass panel.
Additionally, gaskets formed with materials including urethane, RIM urethane, PVC and the like, often require the use of additional seals or sealants between the modular window assembly and the pinch weld flange of the vehicle in order to effectively exclude water, dirt, dust and the like from entering the vehicle. However, the use of such additional seals adds complexity, labor and expense to the vehicle assembly process.
Accordingly, a need exists in the vehicle industry for a modular vehicle window assembly which incorporates a gasket material suitable for formation of gaskets on one, two or three sides of the sheet window panel, for incorporation of fasteners which allow attachment of the assembly mechanically to the vehicle, and for elimination of the need for additional seals. In addition, the gasket material desirably should allow for a reduction in costs, and provide a reliable, high-strength bond between the window panel surface and gasket for long-term security in attachment of windows to the vehicles and wherein the gasket materials exhibit low to moderate compression set, good flexibility and resiliency, good low temperature operating characteristics, and good creep resistance.